The present invention relates to an image input device capable of measuring distance information and color information independently by using a laser range finder and a camera, and more particularly, to an image input device and a calibration method, which are capable of measuring laser light from a laser range finder by using a camera to calibrate a relative position and a relative posture of the camera with respect to the laser range finder.
Examples of a technique of calibrating a laser range finder and a camera include technologies described in Kazuhisa Inaba, Dinesh Manandhar and Ryosuke Shibasaki, Calibration of a Vehicle-based Laser/CCD Sensor System for Urban 3D Mapping, In Proc of the Asian Conference on Remote Sensing 1999, 1999 (hereinafter, referred to as Non-Patent Document 1) and Japanese Patent Laid-open Publication No. H 7-208913 (hereinafter, referred to as Patent Document 1).
According to Non-Patent Document 1, a target serving as both a laser range finder calibration target and a camera calibration target is measured by a laser range finder and a camera, respectively. Based on results of measurement, a relative position and a relative posture between the laser range finder and the camera are calibrated.
According to Patent Document 1, a change in position  of spot light of a laser when a special tool prepared for calibration is moved while being irradiated with the laser light is measured. Based on results of measurement, a relative position and a relative posture between a projector of the laser light and a camera are calculated to manually calibrate the relative position and the relative posture between the projector and the camera.
According to the above-described related art, it is necessary to prepare a special target or a special tool for calibrating the relative position and the relative posture between the laser and the camera.